MIAMI , Florida -LRB- CNN -RRB- -- Hurricane Bertha -- the first hurricane of the 2008 Atlantic season -- increased in strength Monday evening , according to the National Hurricane Center .

A satellite picture from 5:45 a.m. ET Monday shows Hurricane Bertha over the Atlantic .

While Bertha 's power may fluctuate over the next day , it is expected to begin gradually weakening by Wednesday , the center 's 11 p.m. ET advisory said .

Bertha 's became a major -- or Category 3 -- hurricane Monday afternoon . A Category 3 has wind speeds of 111 to 130 mph .

As of 11 p.m. ET , Bertha was 695 miles -LRB- 1,115 km -RRB- east-northeast of the northern Leeward Islands and about 1,085 miles -LRB- 1,745 km -RRB- southeast of Bermuda . The eye was moving toward the west-northwest at about 12 mph . Its maximum sustained winds were clocked at 120 mph -LRB- 195 km/hr -RRB- , up from the 115 mph mentioned in a 5 p.m. advisory .

The hurricane is expected to turn to the northwest and decrease its forward speed in the next 24 to 48 hours , the center said .

There is a very small chance Bertha will make landfall in the United States . Bermuda could be affected by the hurricane this weekend . See Bertha 's projected path ''

`` It is still way too soon to determine whether or not Bertha will affect Bermuda , '' the center said .

The storm formed Thursday in the far eastern Atlantic , off the coast of Africa , near the southern Cape Verde Islands . It strengthened into a hurricane early Monday . Learn more about hurricanes ''

The first tropical storm of the season , Arthur , formed May 31 near the coast of Belize and dumped heavy rain on Central America and southern Mexico .

@highlight

NEW : Bertha 's winds increase from 115 mph to 120 mph

@highlight

Bermuda could be affected by the hurricane this weekend

@highlight

Likelihood of storm making landfall in U.S. is very small

@highlight

Bertha is the first hurricane of the 2008 Atlantic hurricane season